Volatile fuel & organic compound production by Ascocoryne sarcoides : exploration of environmental variables and analytical methods

Abstract

Ascocoryne sarcoides is an endophytic filamentous fungus isolated from Northern Patagonia that can produce petroleum-like fuel compounds directly from cellulose (Strobel et al., 2008). The aim of this project was to study volatile organic compound production by A. sarcoides. The project is different from many other cellulosic biofuel projects that explore alcohol production from pre-treated biomass fermentation. It focuses on the ability of A. sarcoides to convert cellulose and related simple sugars to fuel-related hydrocarbons. The influence of environmental conditions on the growth characteristics and compounds produced from normal metabolic processes was explored. Quantification of volatile production from growth on glucose showed the major compounds were ethanol and acetaldehyde, with the remainder of volatiles near 2 ppm from a continuously aerated culture. These volatiles included compounds of fuel-interest such as benzaldehyde, nonanal, 1-octen-3-ol and 1-butanol, 3-methyl-. Notable compounds with fuel related properties included isopentane, d-limonene, and cyclopropane, propyl-. These compounds all have octane ratings greater than 90 and enthalpies of combustion greater than 3200 kJ mol -1. Oxygen availability influenced the type and number of volatile compounds produced. For example, growth on a soluble cellulose substrate produced greater numbers of volatile compounds at oxygen limited concentrations and more alcohols, alkanes, aromatics, ketones, and esters were identified from mass spectrometry data. In addition, the oxygen availability influenced growth characteristics with a starting oxygen concentration of 7% was low enough to greatly inhibit growth. The growth substrate had a marked influence on the volatile compounds produced. A. sarcoides growth on microcrystalline cellulose produced a greater variety of hydrocarbon compounds compared to growth on glucose, and the highest yield of volatile organics was estimated at 105 mg (g biomass) -1 from the cellulose substrate. The fungus A. sarcoides demonstrated production of valuable fuel compounds on multiple carbon sources. Further work should carry on the analysis of culturing conditions and include evaluation of hydrocarbon yields on pre-treated cellulosic biomass. Studies of this nature should continue to advance knowledge of fungal biological potential for industrial processes.